Upon arrival at the "cuvier" (vathouse) the stalks are removed from the bunches and the grapes crushed. The juice, pips and skins are then lightly pumped into the fermentations vats, following three criterea : geographical parcel origin, the age of the vines and the grape varieties. The alcoholic fermentation usually takes about a week. Then the maceration (with all the skins and pips) lasts an extra three weeks. These transformations take place in thermostatically controled stainless steel vats. After this period of four weeks, the wine is removed from the vats in order to be seperated it from the"marc" (composed largely of the grape skins). It is then returned to clean vats to undergo the malolactic fermentation which transforms the malic acid in the wine into lactic acid. This benefits the wine by making it rounder, more supple with added of finesse. Once both fermentations are completed, frequent tastings are held to decide the final destination of each vat into one of the three wines : Château Latour, Forts de Latour or generic Pauillac. The wine is finally drawn off into oak casks in December. Then the maturing in barrel starts, and will last about 18 months. Until the beginning of the summer following the vintage, the wine remains in the first year cellar, but the barrels are not sealed. Instead, a glass stopper is placed over the bung hole which allows for the gaseous exchange to continue between the wine and the atmosphere. Absorption of wine into the wood as well as evaporation combine to reduce the level in the cask, this requires regular (twice weekly) replacement and is known as "ouillage" (topping up). Also, approximately every three months the cask has to be racked, an operation which involves separating the clear wine from the lees at the bottom. Each wine is thus racked 6 times. In July, before the heat of the summer sets in, the casks are transferred to the underground cellar (or second-year cellar), so that the wine may continue its ageing exposed to small fluctuations of temperature. The casks are positionned with the wooden bung turned to the side, in such a way that the bung remains immersed in the wine, causing the wood to swell and therefore creating a hermetic seal. Thereafter, the topping up is no longer necessary. Racking, however, must be continued every three months. Finally, during the course of the following winter, the wine is fined. The fining allows the collection of the remaining particles which are in suspension in the wine and draw them to the bottom of the cask.  One month before bottling, the wine undergoes its last racking and is then transferred into vats, where the final blending will take place before bottling.